Newtonian improvements  
The scope that has been used for imaging so far has been the 6" reflector. The 10" is a bit too big for the EQ6 mount, but a larger mount is on order.
To prepare for it, certain modifications to the 10" have been made.

The inside of the tube had been painted with matt-black paint. Dark though this might be, stray light reflecting from sources such as the Moon or planets such as Jupiter or Saturn, could bounce around inside the tube and end up in the eyepiece. At worst this would cause visible flaring, and at best, a loss of contrast.
A solution is to coat the inside of the tube with 'flocking material', which consists of many short black fibres. In theory, the fibres are synthetic and do not shed and end up on the mirror. The flocking was obtained from Telescope Parts UK.

The picture shows the tube after one sheet has been applied.The difference between the light reflected by the flocking and the black paint is startling.

The flocking already has an adhesive attaching it to a plastic backing sheet. Removing the whole sheet from the backing would end up with an unmanageable sticky problem, so I decided to leave the backing sheet in place and glue that to the scope interior.

Easier said than done!
Any slight distortion causes ripples and bubbles, which are very difficult to remove. The tube is so long that I can only just reach inside to the centre. Contact adhesive bonds instantly and there is then no easy way to correct mistakes.
However, once the plastic backing is glued securely, the corners of the flocking can be peeled back and then cuts can be made in the plastic backing to make the creases lie down. The flocking can then be carefully lowered back onto the backing sheet. Imperfections are purely cosmetic, but I still spent many hours trying to produce a flat flocked surface. 

Two sheets in place...
  Three sheets...  

And finally completed.
Not a pleasant job to do because it is awkward and prone to disaster!

Secondary mirror supports

On the few pictures taken with the 10" it was seen that the diffraction spikes around bright stars were split.

This is caused by the vanes holding the secondary mirror not being aligned correctly. Ideally each spike should be at 90 degrees to its neighbours. Visual inspection of the vanes showed that this was far from the case.

The secondary was detached and the vanes removed from the tube. The vanes were straightened, and the screw holes in the tube were repositioned.
Angles were checked to be as close to 90 degrees as possible, and the vanes reinserted. Care was taken to get the centre of the secondary holder as close to the centre of the tube as possible. Maximum error as measured with digital vernier calipers was+- 1.6mm.

This is a photograph of the adjusted vanes in situ.

Niels Noordhoek's Maskulator software was used to simulate the diffraction pattern produced by the above picture.

The spikes should not be split!

It will be interesting to see what actual images look like, and a comparison with the simulation can be made.

28th October

Clear sky at last to try out the flocking, the new focus mount, and improved collimation.

  30 second frame of Altair

Encouraging result!

The spikes are at 90 degrees to each other and not split.
The image was unguided and stars are quite small.

  The equivalent taken with the 6 inch reflector (3 vanes) - also 30 second exposure.


The success of the flocking in the 10" reflector prompted me to renovate the small scope. This is after applying the flocking.
The focuser needs to be aligned with the centre of the tube. This was done by wrapping paper around the inside of the tube with a line exactly at the half way point. The laser collimator dot shows up neatly on the line.
The 6" mirror after washing and replacing in the plywood cell. The mirror was made and aluminised in 1985 and apart from a few small blemishes, it is still looking quite good.